INTRODUCTION
Stoeba Sollas, Reference Sollas1888 was created for Samus simplex Carter, Reference Carter1880, an encrusting sponge that fills cavities in calcareous substrates with spiculation composed exclusively of short-shafted dichotriaenes and sanidasters. Several authors have subsequently merged Stoeba with Dercitus Gray, Reference Gray1867 (e.g. von Lendenfeld, Reference von Lendenfeld1903; Topsent, Reference Topsent1904; Desqueyroux-Faúndez & van Soest, Reference Desqueyroux-Faúndez and van Soest1997). According to van Soest et al. (Reference van Soest, Beglinger and De Voogd2010) Dercitus and Stoeba possess this limited set of calthrops and (dicho-)calthrops megascleres spicules, but some species allegedly have a complement of rare oxeas. Dercitus possesses toxa-like spicules, which are lacking in Stoeba. This is the single difference between these genera. In the last morphological revision of the Order Astrophorida, van Soest et al. (Reference van Soest, Beglinger and De Voogd2010) allocated Stoeba as subgenus of Dercitus and listed 15 valid species: Dercitus (Stoeba) syrmatitus de Laubenfels, Reference de Laubenfels1930 and Dercitus (Stoeba) reptans Desqueyroux-Faúndez & van Soest, Reference Desqueyroux-Faúndez and van Soest1997 from Tropical Eastern Pacific; Dercitus (Stoeba) bahamensis van Soest et al., Reference van Soest, Beglinger and De Voogd2010, Dercitus (Stoeba) latex (Moraes & Muricy, Reference Moraes and Muricy2007), Dercitus (Stoeba) verdensis van Soest et al., Reference van Soest, Beglinger and De Voogd2010 and Dercitus (Stoeba) senegalensis van Soest et al., Reference van Soest, Beglinger and De Voogd2010 from Tropical Atlantic; Dercitus (Stoeba) dissimilis (Sarà, Reference Sarà1959), Dercitus (Stoeba) lesinensis (von Lendenfeld, Reference von Lendenfeld1894) and Dercitus (Stoeba) plicatus (Schmidt, Reference Schmidt1868) from Temperate Northern Atlantic; Dercitus (Stoeba) extensus (Dendy, Reference Dendy and Herdman1905) and Dercitus (Stoeba) simplex (Carter, Reference Carter1880) from Western Indo-Pacific; Dercitus (Stoeba) fijiensis van Soest et al., Reference van Soest, Beglinger and De Voogd2010, Dercitus (Stoeba) pauper Sollas, Reference Sollas1902 and Dercitus (Stoeba) xanthus Sutcliffe et al., Reference Sutcliffe, Hooper and Pitcher2010 from Central Indo Pacific and Dercitus (Stoeba) occultus Hentschel, Reference Hentschel, Michaelsen and Hartmeyer1909 from Temperate Australasia.
In this study, a new species of Dercitus (Stoeba) is described from north-east Brazil, increasing to six the number of known species in the Atlantic.
MATERIALS AND METHODS
Specimens were collected during a faunistic survey conducted in the area of the Carapibus beach (Conde city), situated in the Paraíba State coastline, north-eastern Brazil (Figure 1). Specimens were preserved in 80% ethanol and deposited in Coleção de Invertebrados Paulo Young of Universidade Federal da Paraíba (CIPY-UFPB). Dissociated spicule mounts and skeletal sections were made using classical procedures for Demospongiae (Hajdu et al., Reference Hajdu, Peixinho and Fernandez2011). A minimum of 30 spicules of each category were measured (minimum-average-maximum). Images of specimens, sections and SEM preparations were obtained digitally. The classification followed in this work is that proposed by van Soest et al. (Reference van Soest, Beglinger and De Voogd2010). Taxonomic comparisons were made with data tabulated for all species of Dercitus (Stoeba) available in the World Porifera Database (van Soest et al., Reference van Soest, Boury-Esnault, Hooper, Rützler, de Voogd, Alvarez de Glasby, Hajdu, Pisera, Manconi, Schoenberg, Janussen, Tabachnick, Klautau, Picton, Kelly, Vacelet, Dohrmann and Díaz2014). The citations in species presentation are the original descriptions available, completed with the most recent publications giving a good description. Abbreviations used: Porifera Collection of the Museu Nacional, Universidade Federal do Rio de Janeiro (MNRJ); Scanning Electron Microscopy (SEM); Station Marine d'Endoume Collection (SME); Porifera Collection of the Departamento de Zoologia, Instituto de Biologia, Universidade Federal do Rio de Janeiro (UFRJPOR).
Fig. 1. Location of the collection site (Carapibus beach, Conde city) of Dercitus (Stoeba) pseudodiscorhabda sp. nov.
SYSTEMATICS
Phylum PORIFERA Grant, 1836
Order ASTROPHORIDA Sollas, Reference Sollas1888
Family PACHASTRELLIDAE Carter, 1875
Genus Dercitus Gray, Reference Gray1867
Definition
Pachastrellidae with calthrops or dichocalthrops as megascleres and possessing irregular acanthomicrorhabd-like sanidasters with a thick central axis relative to the actines; further microscleres may include smooth toxa-like forms and aster-like compressed forms; no structural oxea megascleres (van Soest et al., Reference van Soest, Beglinger and De Voogd2010).
Subgenus Stoeba Dendy, Reference Dendy and Herdman1905
Definition
Dercitus with a single microsclere category in the form of irregular sanidasters (van Soest et al., Reference van Soest, Beglinger and De Voogd2010).
Type species: Samus simplex Carter, Reference Carter1880.
TYPE MATERIAL
Holotype: CIPY-UFPB 151 – Carapibus beach (7°18′59″S 34°48′54″W), Conde city, Paraíba State, Brazil, shallow water, coll. LIPY crew (Laboratório de Invertebrados Paulo Young), 8 March 2008.
Table 1. Comparative micrometric data on the spicules and overview of distribution of the living species of Dercitus (Stoeba). Values are in micrometres (µm), expressed as follows: minimum – maximum or minimum–average–maximum length/width. Prot. = protocladi; Deut. = deuterocladi. References are numbered and listed after the table.
References: (1) van Soest et al. (Reference van Soest, Beglinger and De Voogd2010); (2) Moraes & Muricy (Reference Moraes and Muricy2007); (3) Present work - MNRJ 7865; (4) Present work - MNRJPOR 628; (5) Present work - UFRJPOR 3254. (6) Maldonado (Reference Maldonado, Hooper and Van Soest2002); (7) Sutcliffe et al. (Reference Sutcliffe, Hooper and Pitcher2010).
COMPARATIVE MATERIAL
MNRJ 7865 (Paratype of Stoeba latex) – Ilha do Meio Cave, Fernando de Noronha Archipelago, Pernambuco State, Brazil, 03°52′S 32°25′W, 8 m depth, coll. E. Hajdu, 16 November 2003. MNRJ 628 (Dercitus plicatus) – Cabo Verde Islands, Branco, 98 m depth, coll. R.W.M. van Soest, HMS CANCAP 7 exp. (#156/045), 5 September 1986. UFRJPOR 3254 (Dercitus plicatus) – Collection SME, det. C. Lévi.
DIAGNOSIS
It is the only Dercitus (Stoeba) with four-rayed calthrops and discorhabd-like sanidasters.
DESCRIPTION
Irregular shape with 3.5 mm long and 1.5 mm wide. Conulose surface, oscules not visible. Consistency hard, brittle. Live colour white and whitish beige in ethanol (Figure 2A, B).
Fig. 2. Dercitus (Stoeba) pseudodiscorhabda sp. nov.: (A, B) Different regions (external and internal) of the holotype (CIPY-UFPB 151) showing calthrops. Scale bars: A, B, 1 mm.
Skeleton
There is no definable structure in either the ectosomal or choanosomal skeletons. Only small fragments of choanosomal tissue attached to shiny, ectosomal layer (see Figure 2B). Sanidasters and calthrops are scattered throughout the sponge with no particular organization, but in high concentrations.
Spicules
Calthrops are regular (Figure 3A, Table 1), in a wide range of sizes; most are regular four-claded equal-length spicules, occasional bifid cladi or with angulated curve: cladi 48–204.6–382 µm, cladome 96–335.1–478 µm.
Fig. 3. Scanning electron microscopy images of spicules of the holotype (CIPY-UFPB 151) of Dercitus (Stoeba) pseudodiscorhabda sp. nov. (A) various calthrops shapes (arrow point to sanidaster-S.); (B) various sanidaster shapes; (C) detail of the ending of two sanidasters. Scale bars: A, 200 µm; B, 5 µm; C, 2 µm.
Straight sanidasters (Figure 3B, C), with blunt endings, straight central shaft, with microspined spines well developed along the whole shaft, generally resembling discorhabds at low magnifications. Pattern of microspination varies along the length of the spicule, being light and irregular on the shaft, becoming more concentrated at the tip and on the edge: 9–15.8–21 µm.
DISTRIBUTION
At present, Dercitus (Stoeba) pseudodiscorhabda sp. nov. is known only from the type locality (Carapibus beach, Paraíba State, Brazil), probably on shallow water, in cavities of calcareous substrata.
ETYMOLOGY
The specific name refers to the occurrence of sanidasters similar to discorhabds.
DISCUSSION
This new species is assigned to Dercitus (Stoeba) based on the presence of a single microsclere category in the form of irregular sanidasters.
There are 17 other described species (including the two unnamed species) of Dercitus (Stoeba), of which 11 differ to D. (S.) pseudodiscorhabda sp. nov. by the presence of dichocalthrops: D. (S.) bahamensis, D. (S.) dissimilis, D. (S.) extensus, D. (S.) fijiensis, D. (S.) lesinensis, D. (S.) occultus, D. (S.) pauper, D. (S.) plicatus, D. (S.) reptans, D. (S.) simplex and D. (S.) verdensis. The other six species contain only calthrops and sanidasters like the new species: D. (S.) latex, D. (S.) senegalensis, D. (S.) syrmatitus, D. (S.) xanthus, D. (S.) sp. van Soest et al. (Reference van Soest, Beglinger and De Voogd2010 from Bonaire) and D. (S.) sp. van Soest et al. (Reference van Soest, Beglinger and De Voogd2010 from Madagascar).
The species most similar to D. (S.) pseudodiscorhabda sp. nov. is D. (S.) syrmatitus, because both have discorhabd-like sanidasters (as discasters in de Laubenfels, Reference de Laubenfels1932; as amphiaster in van Soest et al., Reference van Soest, Beglinger and De Voogd2010). However, in D. (S.) syrmatitus the sanidasters can vary to acanthomicrostrongyles, which are absent in the new species. Furthermore, the spicules are smaller in D. (S.) syrmatitus than in the new species, with sanidasters ranging from 8–12 µm, and calthrops 25–80 µm against sanidasters 10–21 µm, and calthrops 48–382 µm in the new species. Finally, in D. (S.) syrmatitus, the four-rayed calthrops are often reduced to tripods vs regular four-rayed calthrops in D. (S.) pseudodiscorhabda sp. nov.
Although they share the same biogeographic province, D. (S.) latex differ from new species in many features: the spicules of the former are smaller than in new species (sanidasters: 10–15 µm vs 10–21 µm, and calthrops: 42.5–212.5 µm vs 48–382 µm, respectively); in D. (S.) latex the sanidasters are long and thin without microspinations and the calthrops are irregularly curved against discorhabd-like sanidaster with microspinations and regular and straight calthrops in D. (S.) pseudodiscorhabda sp. nov. Finally, D. (S.) latex is reddish-brown with smooth surface against white colour with conulose surface in new species.
Dercitus (Stoeba) senegalensis share with the new species the size of the spicules (see Table 1), the colour (dirty white) and habit (encrusting sponge). However, both differ in morphology of the sanidasters (with spines equally distributed in the shaft in D. (S.) senegalensis against discorhabd-like, with spines concentrated in two areas of shaft in D. (S.) pseudodiscorhabda sp. nov.) and of calthrops (five-claded in D. (S.) senegalensis against four-claded in D. (S.) pseudodiscorhabda sp. nov.). These features also are not found in Dercitus (Stoeba) xanthus, which differs by the red to yellow colour, massive growth form, presence of two categories of three rayed triods (22–26 µm and 49–94 µm) and sanidasters with spines equally distributed in the shaft (10–20 µm). In Dercitus (Stoeba) sp. (from Bonaire) the calthrops are smaller (39–186 µm) than in the new species (48–382 µm) and the sanidasters are not discorhabd-like. Finally, Dercitus (Stoeba) sp. (from Madagascar) is a yellow species with smaller spicules (calthrops 50–250 µm and sanidasters 12.5 µm) and without discorhabd-like sanidaster.
ACKNOWLEDGEMENTS
We thank Dr Guilherme Muricy (Museu Nacional, Universidade Federal do Rio Janeiro) for the loan of comparative materials. We also thank Dr Martin Christoffersen (Coleção de Invertebrados Paulo Young, Universidade Federal da Paraíba) for the loan of the holotype of Dercitus (Stoeba) pseudodiscorhabda sp. nov. Authors are also thankful to Dr Janaina Melo and Diego Maia for SEM facilities at CETENE (Centro de Tecnologias Estratégicas do Nordeste), Thaynã Cavalcanti, Adélia Alliz, MSc Ralf Cordeiro, MSc Daniele Mariz, Dr Carlos Perez (Universidade Federal de Pernambuco-UFPE) and to Dr André Esteves (UFPE) for technical support. We thank two anonymous reviewers for the manuscript review.
FINANCIAL SUPPORT
G.G.S. and U.P. are grateful to CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior), CNPq (Conselho Nacional de Desenvolvimento Científico e Tecnológico – Edital PROTAX: 562320/2010-5) and FACEPE (Fundação de Amparo à Ciência e Tecnologia do Estado de Pernambuco), for providing grants and/or scholarship.
